﻿using System;
using System.IO;
using System.Collections.Generic;
using System.Text;

namespace Poi.NET.util
{
/**
 *  a utility class for handling little-endian numbers, which the 80x86 world is
 *  replete with. The methods are all static, and input/output is from/to byte
 *  arrays, or from InputStreams.
 *
 *@author     Marc Johnson (mjohnson at apache dot org)
 *@author     Andrew Oliver (acoliver at apache dot org)
 *Adapted by Josh Fornwall
 */
public class LittleEndian : LittleEndianConsts {

    private LittleEndian() {
        // no instances of this class
    }

    /**
     *  get a short value from a byte array
     *
     *@param  data    the byte array
     *@param  offset  a starting offset into the byte array
     *@return         the short (16-bit) value
     */
    public static short getShort(byte[] data, int offset) {
        int b0 = data[offset] & 0xFF;
        int b1 = data[offset+1] & 0xFF;
        return (short) ((b1 << 8) + (b0 << 0));
    }


    /**
     *  get an unsigned short value from a byte array
     *
     *@param  data    the byte array
     *@param  offset  a starting offset into the byte array
     *@return         the unsigned short (16-bit) value in an integer
     */
    public static int getUShort(byte[] data, int offset) {
        int b0 = data[offset] & 0xFF;
        int b1 = data[offset+1] & 0xFF;
        return (b1 << 8) + (b0 << 0);
    }

    /**
     *  get a short value from the beginning of a byte array
     *
     *@param  data  the byte array
     *@return       the short (16-bit) value
     */
    public static short getShort(byte[] data) {
        return getShort(data, 0);
    }

    /**
     *  get an unsigned short value from the beginning of a byte array
     *
     *@param  data  the byte array
     *@return       the unsigned short (16-bit) value in an int
     */
    public static int getUShort(byte[] data) {
        return getUShort(data, 0);
    }

    /**
     *  get an int value from a byte array
     *
     *@param  data    the byte array
     *@param  offset  a starting offset into the byte array
     *@return         the int (32-bit) value
     */
    public static int getInt(byte[] data, int offset) {
        int i=offset;
        int b0 = data[i++] & 0xFF;
        int b1 = data[i++] & 0xFF;
        int b2 = data[i++] & 0xFF;
        int b3 = data[i++] & 0xFF;
        return (b3 << 24) + (b2 << 16) + (b1 << 8) + (b0 << 0);
    }


    /**
     *  get an int value from the beginning of a byte array
     *
     *@param  data  the byte array
     *@return the int (32-bit) value
     */
    public static int getInt(byte[] data) {
        return getInt(data, 0);
    }


    /**
     *  get an unsigned int value from a byte array
     *
     *@param  data    the byte array
     *@param  offset  a starting offset into the byte array
     *@return         the unsigned int (32-bit) value in a long
     */
    public static long getUInt(byte[] data, int offset) {
        long retNum = getInt(data, offset);
        return retNum & 0x00FFFFFFFF;
    }

    /**
     *  get an unsigned int value from a byte array
     *
     *@param  data    the byte array
     *@return         the unsigned int (32-bit) value in a long
     */
    public static long getUInt(byte[] data) {
        return getUInt(data,0);
    }

    /**
     *  get a long value from a byte array
     *
     *@param  data    the byte array
     *@param  offset  a starting offset into the byte array
     *@return         the long (64-bit) value
     */
    public static ulong getLong(byte[] data, int offset) {
        ulong result = 0;
		
		for (int j = offset + LittleEndianConsts.LONG_SIZE - 1; j >= offset; j--) {
		    result <<= 8;
		    result |= 0xff & (ulong)data[j];
		}
		return result;
    }

    /**
     *  get a double value from a byte array, reads it in little endian format
     *  then converts the resulting revolting IEEE 754 (curse them) floating
     *  point number to a happy java double
     *
     *@param  data    the byte array
     *@param  offset  a starting offset into the byte array
     *@return         the double (64-bit) value
     */
    public static double getDouble(byte[] data, int offset) {
        return (double)(getLong(data, offset));
    }

    /**
     *  put a short value into a byte array
     *
     *@param  data    the byte array
     *@param  offset  a starting offset into the byte array
     *@param  value   the short (16-bit) value
     */
    public static void putShort(byte[] data, int offset, short value) {
        int i = offset;
        data[i++] = (byte)((value >>  0) & 0xFF);
        data[i++] = (byte)((value >>  8) & 0xFF);
    }

    /**
     * executes:<p/>
     * <code>
     * data[offset] = (byte)value;
     * </code></p>
     * Added for consistency with other put~() methods
     */
    public static void putByte(byte[] data, int offset, int value) {
        data[offset] = (byte) value;
    }

    /**
     * put an unsigned short value into a byte array
     *
     * @param data the byte array
     * @param offset a starting offset into the byte array
     * @param value the short (16-bit) value
     *
     * @exception ArrayIndexOutOfBoundsException may be thrown
     */
    public static void putUShort(byte[] data, int offset, int value) {
        int i = offset;
        data[i++] = (byte)((value >>  0) & 0xFF);
        data[i++] = (byte)((value >>  8) & 0xFF);
    }

    /**
     *  put a short value into beginning of a byte array
     *
     *@param  data   the byte array
     *@param  value  the short (16-bit) value
     */
    public static void putShort(byte[] data, short value) {
        putShort(data, 0, value);
    }


    /**
     *  put an int value into a byte array
     *
     *@param  data    the byte array
     *@param  offset  a starting offset into the byte array
     *@param  value   the int (32-bit) value
     */
    public static void putInt(byte[] data, int offset, int value) {
        int i = offset;
        data[i++] = (byte)((value >>  0) & 0xFF);
        data[i++] = (byte)((value >>  8) & 0xFF);
        data[i++] = (byte)((value >> 16) & 0xFF);
        data[i++] = (byte)((value >> 24) & 0xFF);
    }


    /**
     *  put an int value into beginning of a byte array
     *
     *@param  data   the byte array
     *@param  value  the int (32-bit) value
     */
    public static void putInt(byte[] data, int value) {
        putInt(data, 0, value);
    }


    /**
     *  put a long value into a byte array
     *
     *@param  data    the byte array
     *@param  offset  a starting offset into the byte array
     *@param  value   the long (64-bit) value
     */
    public static void putLong(byte[] data, int offset, long value) {
        int limit = LittleEndianConsts.LONG_SIZE + offset;
        long v = value;
        
        for (int j = offset; j < limit; j++) {
            data[j] = (byte) (v & 0xFF);
            v >>= 8;
        }
    }


    /**
     *  put a double value into a byte array
     *
     *@param  data    the byte array
     *@param  offset  a starting offset into the byte array
     *@param  value   the double (64-bit) value
     */
    public static void putDouble(byte[] data, int offset, double value) {
        putLong(data, offset, (long)value);
    }


    /**
     *  Exception to handle buffer underruns
     *
     *@author     Marc Johnson (mjohnson at apache dot org)
     */
    public readonly class BufferUnderrunException : IOException 
    {
        public BufferUnderrunException() : base("buffer underrun") { }
    }


    /**
     *  get a short value from an InputStream
     *
     *@param  stream the InputStream from which the short is to be read
     *@return                              the short (16-bit) value
     *@exception  IOException              will be propagated back to the caller
     *@exception  BufferUnderrunException  if the stream cannot provide enough bytes
     */
    public static short readShort(StreamReader stream) {

        return (short) readUShort(stream);
    }

    public static int readUShort(StreamReader stream) {

        int ch1 = stream.Read();
        int ch2 = stream.Read();
        if ((ch1 | ch2) < 0) {
            throw new BufferUnderrunException();
        }
        return (ch2 << 8) + (ch1 << 0);
    }
    

    /**
     *  get an int value from an InputStream
     *
     *@param  stream the InputStream from which the int is to be read
     * @return                              the int (32-bit) value
     * @exception  IOException              will be propagated back to the caller
     * @exception  BufferUnderrunException  if the stream cannot provide enough bytes
     */
    public static int readInt(StreamReader stream) {
        int ch1 = stream.Read();
        int ch2 = stream.Read();
        int ch3 = stream.Read();
        int ch4 = stream.Read();
        if ((ch1 | ch2 | ch3 | ch4) < 0) {
            throw new BufferUnderrunException();
        }
        return (ch4 << 24) + (ch3<<16) + (ch2 << 8) + (ch1 << 0);
    }
   

    /**
     *  get a long value from an InputStream
     *
     * @param  stream the InputStream from which the long is to be read
     * @return                              the long (64-bit) value
     * @exception  IOException              will be propagated back to the caller
     * @exception  BufferUnderrunException  if the stream cannot provide enough bytes
     */
    public static long readLong(StreamReader stream) {
        int ch1 = stream.Read();
        int ch2 = stream.Read();
        int ch3 = stream.Read();
        int ch4 = stream.Read();
        int ch5 = stream.Read();
        int ch6 = stream.Read();
        int ch7 = stream.Read();
        int ch8 = stream.Read();
        if ((ch1 | ch2 | ch3 | ch4 | ch5 | ch6 | ch7 | ch8) < 0) {
            throw new BufferUnderrunException();
        }
        
        return 
            ((long)ch8 << 56) +
            ((long)ch7 << 48) +
            ((long)ch6 << 40) +
            ((long)ch5 << 32) +
            ((long)ch4 << 24) + // cast to long to preserve bit 31 (sign bit for ints)
                  (ch3 << 16) +
                  (ch2 <<  8) +
                  (ch1 <<  0);
    }

    /**
     *  Convert an 'unsigned' byte to an integer. ie, don't carry across the
     *  sign.
     *
     * @param  b  Description of the Parameter
     * @return    Description of the Return Value
     */
    public static int ubyteToInt(byte b) {
        return b & 0xFF;
    }


    /**
     *  get the unsigned value of a byte.
     *
     * @param  data    the byte array.
     * @param  offset  a starting offset into the byte array.
     * @return         the unsigned value of the byte as a 32 bit integer
     */
    public static int getUnsignedByte(byte[] data, int offset) {
        return data[offset] & 0xFF;
    }


    /**
     *  Copy a portion of a byte array
     *
     * @param  data                        the original byte array
     * @param  offset                      Where to start copying from.
     * @param  size                        Number of bytes to copy.
     * @return                             The byteArray value
     * @throws  IndexOutOfBoundsException  - if copying would cause access of
     *      data outside array bounds.
     */
    public static byte[] getByteArray(byte[] data, int offset, int size) {
        byte[] copy = new byte[size];
        Array.Copy(data, offset, copy, 0, size);

        return copy;
    }
}

}
